Ideal percentage of CO2 required for growth of Brucella abortus -

Ans. is 'b' i.e., 5-10% "Addition of 5-10% CO2 improves the growth of B abortus and B. melitensis". - medchrome.com* All Brucella spp. are strictly aerobic, but some B. abortus biovars, some Brucella isolates from marine mammals, and B. ovis only grow in atmospheres containing 5-10% CO2* This does not relate to a decreased PO2 but to a specific requirement of CO2 per se, and at least for the CO2- dependent B. abortus strains, sub-culture frequently leads to selection of spontaneously occurring CO2 independent mutants.* Although the exact redox potential (E) and oxygen tension required for optimal growth are not known the brucellae need vigorous aeration when grown in broth. For small to medium volumes shaking is adequate, but for large volumes spargine and antifoaming agents are necessary.